The overall goal of the studies proposed here is to increase our knowledge of muscarinic cholinergic receptors at the molecular level. We now know from molecular biological experiments that multiple subtypes of these receptors exist. However, due to the fact that no drugs exist that are highly selective for a given subtype, we currently have no tools with which to study the individual subtypes in the presence of any of the other subtypes. Muscarinic receptors are involved in a variety of processes in the human body including memory and learning, thermal regulation, heart rate, Gl secretions etc. Drugs that can selectively affect these processes could be therapeutically useful in the management of Alzheimer's disease, peptic ulcer, hypertension etc. Development of such agents relies on understanding the exact localization and function of the various subtypes. The goals of the current application are: 1. To develop polyclonal and monoclonal antibodies specifically directed against each of the known subtypes of muscarinic cholinergic receptors. 2. To utilize these antibodies to develop assays to quantify subtypes of receptors in homogenates of tissues that contain multiple subtypes. With this assay, to measure the density of each subtype in a number of key organs and brain regions. 3. To utilize these antibodies to determine which parts of the molecule are involved in ligand binding, G-protein interactions, and production of second messengers. These studies will also include tests of the current model of secondary structure of the receptors (i.e. which portions are on the inside of the cell and which are on the outside.) 4. To utilize these antibodies to examine the distribution of receptor subtypes in thin sections of tissue both at the visible and light microscope level.